function Map(el) {

    // 1.保存下地图对象
    this.el = el

    // 2. 记录地图相关属性
    this.width = 800
    this.height = 400
}

Map.prototype.create = function() {
    
    this.el.style.width = this.width + "px"
    this.el.style.height = this.height+ "px"
    this.el.style.background = "url(./bg.png)"
    this.el.style.border = "10px solid green"
    this.el.style.position = "relative"
}